2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
5 \section[TcType]{Types used in the typechecker}
7 This module provides the Type interface for front-end parts of the
10 * treat "source types" as opaque:
11 newtypes, and predicates are meaningful.
12 * look through usage types
14 The "tc" prefix is for "TypeChecker", because the type checker
15 is the principal client.
19 --------------------------------
21 TcType, TcSigmaType, TcRhoType, TcTauType, TcPredType, TcThetaType,
22 TcTyVar, TcTyVarSet, TcKind,
24 BoxyTyVar, BoxySigmaType, BoxyRhoType, BoxyThetaType, BoxyType,
26 --------------------------------
28 UserTypeCtxt(..), pprUserTypeCtxt,
29 TcTyVarDetails(..), BoxInfo(..), pprTcTyVarDetails,
30 MetaDetails(Flexi, Indirect), SkolemInfo(..), pprSkolTvBinding, pprSkolInfo,
31 isImmutableTyVar, isSkolemTyVar, isMetaTyVar, isBoxyTyVar,
32 isSigTyVar, isExistentialTyVar, isTyConableTyVar,
36 --------------------------------
40 --------------------------------
42 -- These are important because they do not look through newtypes
44 tcSplitForAllTys, tcSplitPhiTy,
45 tcSplitFunTy_maybe, tcSplitFunTys, tcFunArgTy, tcFunResultTy, tcSplitFunTysN,
46 tcSplitTyConApp, tcSplitTyConApp_maybe, tcTyConAppTyCon, tcTyConAppArgs,
47 tcSplitAppTy_maybe, tcSplitAppTy, tcSplitAppTys, repSplitAppTy_maybe,
48 tcInstHeadTyNotSynonym, tcInstHeadTyAppAllTyVars,
49 tcGetTyVar_maybe, tcGetTyVar,
50 tcSplitSigmaTy, tcMultiSplitSigmaTy,
52 ---------------------------------
54 -- Again, newtypes are opaque
55 tcEqType, tcEqTypes, tcEqPred, tcCmpType, tcCmpTypes, tcCmpPred, tcEqTypeX,
57 isSigmaTy, isOverloadedTy, isRigidTy, isBoxyTy,
58 isDoubleTy, isFloatTy, isIntTy, isStringTy,
59 isIntegerTy, isBoolTy, isUnitTy, isCharTy,
60 isTauTy, isTauTyCon, tcIsTyVarTy, tcIsForAllTy,
62 ---------------------------------
63 -- Misc type manipulators
65 tyClsNamesOfType, tyClsNamesOfDFunHead,
68 ---------------------------------
70 getClassPredTys_maybe, getClassPredTys,
71 isClassPred, isTyVarClassPred, isEqPred,
72 mkDictTy, tcSplitPredTy_maybe,
73 isPredTy, isDictTy, tcSplitDFunTy, tcSplitDFunHead, predTyUnique,
74 mkClassPred, isInheritablePred, isIPPred,
75 dataConsStupidTheta, isRefineableTy, isRefineablePred,
77 ---------------------------------
78 -- Foreign import and export
79 isFFIArgumentTy, -- :: DynFlags -> Safety -> Type -> Bool
80 isFFIImportResultTy, -- :: DynFlags -> Type -> Bool
81 isFFIExportResultTy, -- :: Type -> Bool
82 isFFIExternalTy, -- :: Type -> Bool
83 isFFIDynArgumentTy, -- :: Type -> Bool
84 isFFIDynResultTy, -- :: Type -> Bool
85 isFFILabelTy, -- :: Type -> Bool
86 isFFIDotnetTy, -- :: DynFlags -> Type -> Bool
87 isFFIDotnetObjTy, -- :: Type -> Bool
88 isFFITy, -- :: Type -> Bool
89 tcSplitIOType_maybe, -- :: Type -> Maybe Type
90 toDNType, -- :: Type -> DNType
92 --------------------------------
93 -- Rexported from Type
94 Kind, -- Stuff to do with kinds is insensitive to pre/post Tc
95 unliftedTypeKind, liftedTypeKind, argTypeKind,
96 openTypeKind, mkArrowKind, mkArrowKinds,
97 isLiftedTypeKind, isUnliftedTypeKind, isSubOpenTypeKind,
98 isSubArgTypeKind, isSubKind, defaultKind,
99 kindVarRef, mkKindVar,
101 Type, PredType(..), ThetaType,
102 mkForAllTy, mkForAllTys,
103 mkFunTy, mkFunTys, zipFunTys,
104 mkTyConApp, mkAppTy, mkAppTys, applyTy, applyTys,
105 mkTyVarTy, mkTyVarTys, mkTyConTy, mkPredTy, mkPredTys,
107 -- Type substitutions
108 TvSubst(..), -- Representation visible to a few friends
109 TvSubstEnv, emptyTvSubst, substEqSpec,
110 mkOpenTvSubst, zipOpenTvSubst, zipTopTvSubst, mkTopTvSubst, notElemTvSubst,
111 getTvSubstEnv, setTvSubstEnv, getTvInScope, extendTvInScope, lookupTyVar,
112 extendTvSubst, extendTvSubstList, isInScope, mkTvSubst, zipTyEnv,
113 substTy, substTys, substTyWith, substTheta, substTyVar, substTyVars, substTyVarBndr,
115 isUnLiftedType, -- Source types are always lifted
116 isUnboxedTupleType, -- Ditto
119 tidyTopType, tidyType, tidyPred, tidyTypes, tidyFreeTyVars, tidyOpenType, tidyOpenTypes,
120 tidyTyVarBndr, tidyOpenTyVar, tidyOpenTyVars, tidySkolemTyVar,
123 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta,
124 tcTyVarsOfType, tcTyVarsOfTypes, exactTyVarsOfType, exactTyVarsOfTypes,
126 pprKind, pprParendKind,
127 pprType, pprParendType, pprTypeApp, pprTyThingCategory,
128 pprPred, pprTheta, pprThetaArrow, pprClassPred
132 #include "HsVersions.h"
165 %************************************************************************
169 %************************************************************************
171 The type checker divides the generic Type world into the
172 following more structured beasts:
174 sigma ::= forall tyvars. phi
175 -- A sigma type is a qualified type
177 -- Note that even if 'tyvars' is empty, theta
178 -- may not be: e.g. (?x::Int) => Int
180 -- Note that 'sigma' is in prenex form:
181 -- all the foralls are at the front.
182 -- A 'phi' type has no foralls to the right of
190 -- A 'tau' type has no quantification anywhere
191 -- Note that the args of a type constructor must be taus
193 | tycon tau_1 .. tau_n
197 -- In all cases, a (saturated) type synonym application is legal,
198 -- provided it expands to the required form.
201 type TcTyVar = TyVar -- Used only during type inference
202 type TcType = Type -- A TcType can have mutable type variables
203 -- Invariant on ForAllTy in TcTypes:
205 -- a cannot occur inside a MutTyVar in T; that is,
206 -- T is "flattened" before quantifying over a
208 -- These types do not have boxy type variables in them
209 type TcPredType = PredType
210 type TcThetaType = ThetaType
211 type TcSigmaType = TcType
212 type TcRhoType = TcType
213 type TcTauType = TcType
215 type TcTyVarSet = TyVarSet
217 -- These types may have boxy type variables in them
218 type BoxyTyVar = TcTyVar
219 type BoxyRhoType = TcType
220 type BoxyThetaType = TcThetaType
221 type BoxySigmaType = TcType
222 type BoxyType = TcType
226 %************************************************************************
228 \subsection{TyVarDetails}
230 %************************************************************************
232 TyVarDetails gives extra info about type variables, used during type
233 checking. It's attached to mutable type variables only.
234 It's knot-tied back to Var.lhs. There is no reason in principle
235 why Var.lhs shouldn't actually have the definition, but it "belongs" here.
238 Note [Signature skolems]
239 ~~~~~~~~~~~~~~~~~~~~~~~~
244 (x,y,z) = ([y,z], z, head x)
246 Here, x and y have type sigs, which go into the environment. We used to
247 instantiate their types with skolem constants, and push those types into
248 the RHS, so we'd typecheck the RHS with type
250 where a*, b* are skolem constants, and c is an ordinary meta type varible.
252 The trouble is that the occurrences of z in the RHS force a* and b* to
253 be the *same*, so we can't make them into skolem constants that don't unify
254 with each other. Alas.
256 One solution would be insist that in the above defn the programmer uses
257 the same type variable in both type signatures. But that takes explanation.
259 The alternative (currently implemented) is to have a special kind of skolem
260 constant, SigTv, which can unify with other SigTvs. These are *not* treated
261 as righd for the purposes of GADTs. And they are used *only* for pattern
262 bindings and mutually recursive function bindings. See the function
263 TcBinds.tcInstSig, and its use_skols parameter.
267 -- A TyVarDetails is inside a TyVar
269 = SkolemTv SkolemInfo -- A skolem constant
271 | MetaTv BoxInfo (IORef MetaDetails)
274 = BoxTv -- The contents is a (non-boxy) sigma-type
275 -- That is, this MetaTv is a "box"
277 | TauTv -- The contents is a (non-boxy) tau-type
278 -- That is, this MetaTv is an ordinary unification variable
280 | SigTv SkolemInfo -- A variant of TauTv, except that it should not be
281 -- unified with a type, only with a type variable
282 -- SigTvs are only distinguished to improve error messages
283 -- see Note [Signature skolems]
284 -- The MetaDetails, if filled in, will
285 -- always be another SigTv or a SkolemTv
288 -- A TauTv is always filled in with a tau-type, which
289 -- never contains any BoxTvs, nor any ForAlls
291 -- However, a BoxTv can contain a type that contains further BoxTvs
292 -- Notably, when typechecking an explicit list, say [e1,e2], with
293 -- expected type being a box b1, we fill in b1 with (List b2), where
294 -- b2 is another (currently empty) box.
297 = Flexi -- Flexi type variables unify to become
300 | Indirect TcType -- INVARIANT:
301 -- For a BoxTv, this type must be non-boxy
302 -- For a TauTv, this type must be a tau-type
304 -- Generally speaking, SkolemInfo should not contain location info
305 -- that is contained in the Name of the tyvar with this SkolemInfo
307 = SigSkol UserTypeCtxt -- A skolem that is created by instantiating
308 -- a programmer-supplied type signature
309 -- Location of the binding site is on the TyVar
311 -- The rest are for non-scoped skolems
312 | ClsSkol Class -- Bound at a class decl
313 | InstSkol -- Bound at an instance decl
314 | FamInstSkol -- Bound at a family instance decl
315 | PatSkol DataCon -- An existential type variable bound by a pattern for
316 -- a data constructor with an existential type. E.g.
317 -- data T = forall a. Eq a => MkT a
319 -- The pattern MkT x will allocate an existential type
321 | ArrowSkol -- An arrow form (see TcArrows)
323 | RuleSkol RuleName -- The LHS of a RULE
324 | GenSkol [TcTyVar] -- Bound when doing a subsumption check for
325 TcType -- (forall tvs. ty)
327 | RuntimeUnkSkol -- a type variable used to represent an unknown
328 -- runtime type (used in the GHCi debugger)
330 | UnkSkol -- Unhelpful info (until I improve it)
332 -------------------------------------
333 -- UserTypeCtxt describes the places where a
334 -- programmer-written type signature can occur
335 -- Like SkolemInfo, no location info
337 = FunSigCtxt Name -- Function type signature
338 -- Also used for types in SPECIALISE pragmas
339 | ExprSigCtxt -- Expression type signature
340 | ConArgCtxt Name -- Data constructor argument
341 | TySynCtxt Name -- RHS of a type synonym decl
342 | GenPatCtxt -- Pattern in generic decl
343 -- f{| a+b |} (Inl x) = ...
344 | LamPatSigCtxt -- Type sig in lambda pattern
346 | BindPatSigCtxt -- Type sig in pattern binding pattern
348 | ResSigCtxt -- Result type sig
350 | ForSigCtxt Name -- Foreign inport or export signature
351 | DefaultDeclCtxt -- Types in a default declaration
352 | SpecInstCtxt -- SPECIALISE instance pragma
354 -- Notes re TySynCtxt
355 -- We allow type synonyms that aren't types; e.g. type List = []
357 -- If the RHS mentions tyvars that aren't in scope, we'll
358 -- quantify over them:
359 -- e.g. type T = a->a
360 -- will become type T = forall a. a->a
362 -- With gla-exts that's right, but for H98 we should complain.
364 ---------------------------------
367 mkKindName :: Unique -> Name
368 mkKindName unique = mkSystemName unique kind_var_occ
370 kindVarRef :: KindVar -> IORef MetaDetails
372 ASSERT ( isTcTyVar tc )
373 case tcTyVarDetails tc of
374 MetaTv TauTv ref -> ref
375 other -> pprPanic "kindVarRef" (ppr tc)
377 mkKindVar :: Unique -> IORef MetaDetails -> KindVar
379 = mkTcTyVar (mkKindName u)
380 tySuperKind -- not sure this is right,
381 -- do we need kind vars for
385 kind_var_occ :: OccName -- Just one for all KindVars
386 -- They may be jiggled by tidying
387 kind_var_occ = mkOccName tvName "k"
391 %************************************************************************
395 %************************************************************************
398 pprTcTyVarDetails :: TcTyVarDetails -> SDoc
400 pprTcTyVarDetails (SkolemTv _) = ptext SLIT("sk")
401 pprTcTyVarDetails (MetaTv BoxTv _) = ptext SLIT("box")
402 pprTcTyVarDetails (MetaTv TauTv _) = ptext SLIT("tau")
403 pprTcTyVarDetails (MetaTv (SigTv _) _) = ptext SLIT("sig")
405 pprUserTypeCtxt :: UserTypeCtxt -> SDoc
406 pprUserTypeCtxt (FunSigCtxt n) = ptext SLIT("the type signature for") <+> quotes (ppr n)
407 pprUserTypeCtxt ExprSigCtxt = ptext SLIT("an expression type signature")
408 pprUserTypeCtxt (ConArgCtxt c) = ptext SLIT("the type of the constructor") <+> quotes (ppr c)
409 pprUserTypeCtxt (TySynCtxt c) = ptext SLIT("the RHS of the type synonym") <+> quotes (ppr c)
410 pprUserTypeCtxt GenPatCtxt = ptext SLIT("the type pattern of a generic definition")
411 pprUserTypeCtxt LamPatSigCtxt = ptext SLIT("a pattern type signature")
412 pprUserTypeCtxt BindPatSigCtxt = ptext SLIT("a pattern type signature")
413 pprUserTypeCtxt ResSigCtxt = ptext SLIT("a result type signature")
414 pprUserTypeCtxt (ForSigCtxt n) = ptext SLIT("the foreign declaration for") <+> quotes (ppr n)
415 pprUserTypeCtxt DefaultDeclCtxt = ptext SLIT("a type in a `default' declaration")
416 pprUserTypeCtxt SpecInstCtxt = ptext SLIT("a SPECIALISE instance pragma")
419 --------------------------------
420 tidySkolemTyVar :: TidyEnv -> TcTyVar -> (TidyEnv, TcTyVar)
421 -- Tidy the type inside a GenSkol, preparatory to printing it
422 tidySkolemTyVar env tv
423 = ASSERT( isSkolemTyVar tv || isSigTyVar tv )
424 (env1, mkTcTyVar (tyVarName tv) (tyVarKind tv) info1)
426 (env1, info1) = case tcTyVarDetails tv of
427 SkolemTv info -> (env1, SkolemTv info')
429 (env1, info') = tidy_skol_info env info
430 MetaTv (SigTv info) box -> (env1, MetaTv (SigTv info') box)
432 (env1, info') = tidy_skol_info env info
435 tidy_skol_info env (GenSkol tvs ty) = (env2, GenSkol tvs1 ty1)
437 (env1, tvs1) = tidyOpenTyVars env tvs
438 (env2, ty1) = tidyOpenType env1 ty
439 tidy_skol_info env info = (env, info)
441 pprSkolTvBinding :: TcTyVar -> SDoc
442 -- Print info about the binding of a skolem tyvar,
443 -- or nothing if we don't have anything useful to say
445 = ASSERT ( isTcTyVar tv )
446 quotes (ppr tv) <+> ppr_details (tcTyVarDetails tv)
448 ppr_details (MetaTv TauTv _) = ptext SLIT("is a meta type variable")
449 ppr_details (MetaTv BoxTv _) = ptext SLIT("is a boxy type variable")
450 ppr_details (MetaTv (SigTv info) _) = ppr_skol info
451 ppr_details (SkolemTv info) = ppr_skol info
453 ppr_skol UnkSkol = empty -- Unhelpful; omit
454 ppr_skol RuntimeUnkSkol = ptext SLIT("is an unknown runtime type")
455 ppr_skol info = sep [ptext SLIT("is a rigid type variable bound by"),
456 sep [pprSkolInfo info,
457 nest 2 (ptext SLIT("at") <+> ppr (getSrcLoc tv))]]
459 pprSkolInfo :: SkolemInfo -> SDoc
460 pprSkolInfo (SigSkol ctxt) = pprUserTypeCtxt ctxt
461 pprSkolInfo (ClsSkol cls) = ptext SLIT("the class declaration for") <+> quotes (ppr cls)
462 pprSkolInfo InstSkol = ptext SLIT("the instance declaration")
463 pprSkolInfo FamInstSkol = ptext SLIT("the family instance declaration")
464 pprSkolInfo (RuleSkol name) = ptext SLIT("the RULE") <+> doubleQuotes (ftext name)
465 pprSkolInfo ArrowSkol = ptext SLIT("the arrow form")
466 pprSkolInfo (PatSkol dc) = sep [ptext SLIT("the constructor") <+> quotes (ppr dc)]
467 pprSkolInfo (GenSkol tvs ty) = sep [ptext SLIT("the polymorphic type"),
468 nest 2 (quotes (ppr (mkForAllTys tvs ty)))]
471 -- For type variables the others are dealt with by pprSkolTvBinding.
472 -- For Insts, these cases should not happen
473 pprSkolInfo UnkSkol = panic "UnkSkol"
474 pprSkolInfo RuntimeUnkSkol = panic "RuntimeUnkSkol"
476 instance Outputable MetaDetails where
477 ppr Flexi = ptext SLIT("Flexi")
478 ppr (Indirect ty) = ptext SLIT("Indirect") <+> ppr ty
482 %************************************************************************
486 %************************************************************************
489 isImmutableTyVar :: TyVar -> Bool
492 | isTcTyVar tv = isSkolemTyVar tv
495 isTyConableTyVar, isSkolemTyVar, isExistentialTyVar,
496 isBoxyTyVar, isMetaTyVar :: TcTyVar -> Bool
499 -- True of a meta-type variable tha can be filled in
500 -- with a type constructor application; in particular,
502 = ASSERT( isTcTyVar tv)
503 case tcTyVarDetails tv of
504 MetaTv BoxTv _ -> True
505 MetaTv TauTv _ -> True
506 MetaTv (SigTv {}) _ -> False
510 = ASSERT( isTcTyVar tv )
511 case tcTyVarDetails tv of
515 isExistentialTyVar tv -- Existential type variable, bound by a pattern
516 = ASSERT( isTcTyVar tv )
517 case tcTyVarDetails tv of
518 SkolemTv (PatSkol {}) -> True
522 = ASSERT2( isTcTyVar tv, ppr tv )
523 case tcTyVarDetails tv of
528 = ASSERT( isTcTyVar tv )
529 case tcTyVarDetails tv of
530 MetaTv BoxTv _ -> True
534 = ASSERT( isTcTyVar tv )
535 case tcTyVarDetails tv of
536 MetaTv (SigTv _) _ -> True
539 metaTvRef :: TyVar -> IORef MetaDetails
541 = ASSERT( isTcTyVar tv )
542 case tcTyVarDetails tv of
544 other -> pprPanic "metaTvRef" (ppr tv)
546 isFlexi, isIndirect :: MetaDetails -> Bool
548 isFlexi other = False
550 isIndirect (Indirect _) = True
551 isIndirect other = False
555 %************************************************************************
557 \subsection{Tau, sigma and rho}
559 %************************************************************************
562 mkSigmaTy :: [TyVar] -> [PredType] -> Type -> Type
563 mkSigmaTy tyvars theta tau = mkForAllTys tyvars (mkPhiTy theta tau)
565 mkPhiTy :: [PredType] -> Type -> Type
566 mkPhiTy theta ty = foldr (\p r -> mkFunTy (mkPredTy p) r) ty theta
569 @isTauTy@ tests for nested for-alls. It should not be called on a boxy type.
572 isTauTy :: Type -> Bool
573 isTauTy ty | Just ty' <- tcView ty = isTauTy ty'
574 isTauTy (TyVarTy tv) = ASSERT( not (isTcTyVar tv && isBoxyTyVar tv) )
576 isTauTy (TyConApp tc tys) = all isTauTy tys && isTauTyCon tc
577 isTauTy (AppTy a b) = isTauTy a && isTauTy b
578 isTauTy (FunTy a b) = isTauTy a && isTauTy b
579 isTauTy (PredTy p) = True -- Don't look through source types
580 isTauTy other = False
583 isTauTyCon :: TyCon -> Bool
584 -- Returns False for type synonyms whose expansion is a polytype
586 | isClosedSynTyCon tc = isTauTy (snd (synTyConDefn tc))
590 isBoxyTy :: TcType -> Bool
591 isBoxyTy ty = any isBoxyTyVar (varSetElems (tcTyVarsOfType ty))
593 isRigidTy :: TcType -> Bool
594 -- A type is rigid if it has no meta type variables in it
595 isRigidTy ty = all isImmutableTyVar (varSetElems (tcTyVarsOfType ty))
597 isRefineableTy :: TcType -> Bool
598 -- A type should have type refinements applied to it if it has
599 -- free type variables, and they are all rigid
600 isRefineableTy ty = not (null tc_tvs) && all isImmutableTyVar tc_tvs
602 tc_tvs = varSetElems (tcTyVarsOfType ty)
604 isRefineablePred :: TcPredType -> Bool
605 isRefineablePred pred = not (null tc_tvs) && all isImmutableTyVar tc_tvs
607 tc_tvs = varSetElems (tcTyVarsOfPred pred)
610 getDFunTyKey :: Type -> OccName -- Get some string from a type, to be used to
611 -- construct a dictionary function name
612 getDFunTyKey ty | Just ty' <- tcView ty = getDFunTyKey ty'
613 getDFunTyKey (TyVarTy tv) = getOccName tv
614 getDFunTyKey (TyConApp tc _) = getOccName tc
615 getDFunTyKey (AppTy fun _) = getDFunTyKey fun
616 getDFunTyKey (FunTy arg _) = getOccName funTyCon
617 getDFunTyKey (ForAllTy _ t) = getDFunTyKey t
618 getDFunTyKey ty = pprPanic "getDFunTyKey" (pprType ty)
619 -- PredTy shouldn't happen
623 %************************************************************************
625 \subsection{Expanding and splitting}
627 %************************************************************************
629 These tcSplit functions are like their non-Tc analogues, but
630 a) they do not look through newtypes
631 b) they do not look through PredTys
632 c) [future] they ignore usage-type annotations
634 However, they are non-monadic and do not follow through mutable type
635 variables. It's up to you to make sure this doesn't matter.
638 tcSplitForAllTys :: Type -> ([TyVar], Type)
639 tcSplitForAllTys ty = split ty ty []
641 split orig_ty ty tvs | Just ty' <- tcView ty = split orig_ty ty' tvs
642 split orig_ty (ForAllTy tv ty) tvs
643 | not (isCoVar tv) = split ty ty (tv:tvs)
644 split orig_ty t tvs = (reverse tvs, orig_ty)
646 tcIsForAllTy ty | Just ty' <- tcView ty = tcIsForAllTy ty'
647 tcIsForAllTy (ForAllTy tv ty) = not (isCoVar tv)
648 tcIsForAllTy t = False
650 tcSplitPhiTy :: Type -> (ThetaType, Type)
651 tcSplitPhiTy ty = split ty ty []
653 split orig_ty ty tvs | Just ty' <- tcView ty = split orig_ty ty' tvs
655 split orig_ty (ForAllTy tv ty) ts
656 | isCoVar tv = split ty ty (eq_pred:ts)
658 PredTy eq_pred = tyVarKind tv
659 split orig_ty (FunTy arg res) ts
660 | Just p <- tcSplitPredTy_maybe arg = split res res (p:ts)
661 split orig_ty ty ts = (reverse ts, orig_ty)
663 tcSplitSigmaTy :: Type -> ([TyVar], ThetaType, Type)
664 tcSplitSigmaTy ty = case tcSplitForAllTys ty of
665 (tvs, rho) -> case tcSplitPhiTy rho of
666 (theta, tau) -> (tvs, theta, tau)
668 -----------------------
671 -> ( [([TyVar], ThetaType)], -- forall as.C => forall bs.D
672 TcSigmaType) -- The rest of the type
674 -- We need a loop here because we are now prepared to entertain
676 -- f:: forall a. Eq a => forall b. Baz b => tau
677 -- We want to instantiate this to
678 -- f2::tau {f2 = f1 b (Baz b), f1 = f a (Eq a)}
680 tcMultiSplitSigmaTy sigma
681 = case (tcSplitSigmaTy sigma) of
682 ([],[],ty) -> ([], sigma)
683 (tvs, theta, ty) -> case tcMultiSplitSigmaTy ty of
684 (pairs, rest) -> ((tvs,theta):pairs, rest)
686 -----------------------
687 tcTyConAppTyCon :: Type -> TyCon
688 tcTyConAppTyCon ty = case tcSplitTyConApp_maybe ty of
690 Nothing -> pprPanic "tcTyConAppTyCon" (pprType ty)
692 tcTyConAppArgs :: Type -> [Type]
693 tcTyConAppArgs ty = case tcSplitTyConApp_maybe ty of
694 Just (_, args) -> args
695 Nothing -> pprPanic "tcTyConAppArgs" (pprType ty)
697 tcSplitTyConApp :: Type -> (TyCon, [Type])
698 tcSplitTyConApp ty = case tcSplitTyConApp_maybe ty of
700 Nothing -> pprPanic "tcSplitTyConApp" (pprType ty)
702 tcSplitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
703 tcSplitTyConApp_maybe ty | Just ty' <- tcView ty = tcSplitTyConApp_maybe ty'
704 tcSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
705 tcSplitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
706 -- Newtypes are opaque, so they may be split
707 -- However, predicates are not treated
708 -- as tycon applications by the type checker
709 tcSplitTyConApp_maybe other = Nothing
711 -----------------------
712 tcSplitFunTys :: Type -> ([Type], Type)
713 tcSplitFunTys ty = case tcSplitFunTy_maybe ty of
715 Just (arg,res) -> (arg:args, res')
717 (args,res') = tcSplitFunTys res
719 tcSplitFunTy_maybe :: Type -> Maybe (Type, Type)
720 tcSplitFunTy_maybe ty | Just ty' <- tcView ty = tcSplitFunTy_maybe ty'
721 tcSplitFunTy_maybe (FunTy arg res) | not (isPredTy arg) = Just (arg, res)
722 tcSplitFunTy_maybe other = Nothing
723 -- Note the (not (isPredTy arg)) guard
724 -- Consider (?x::Int) => Bool
725 -- We don't want to treat this as a function type!
726 -- A concrete example is test tc230:
727 -- f :: () -> (?p :: ()) => () -> ()
733 -> Arity -- N: Number of desired args
734 -> ([TcSigmaType], -- Arg types (N or fewer)
735 TcSigmaType) -- The rest of the type
737 tcSplitFunTysN ty n_args
740 | Just (arg,res) <- tcSplitFunTy_maybe ty
741 = case tcSplitFunTysN res (n_args - 1) of
742 (args, res) -> (arg:args, res)
746 tcSplitFunTy ty = expectJust "tcSplitFunTy" (tcSplitFunTy_maybe ty)
747 tcFunArgTy ty = fst (tcSplitFunTy ty)
748 tcFunResultTy ty = snd (tcSplitFunTy ty)
750 -----------------------
751 tcSplitAppTy_maybe :: Type -> Maybe (Type, Type)
752 tcSplitAppTy_maybe ty | Just ty' <- tcView ty = tcSplitAppTy_maybe ty'
753 tcSplitAppTy_maybe ty = repSplitAppTy_maybe ty
755 tcSplitAppTy :: Type -> (Type, Type)
756 tcSplitAppTy ty = case tcSplitAppTy_maybe ty of
758 Nothing -> pprPanic "tcSplitAppTy" (pprType ty)
760 tcSplitAppTys :: Type -> (Type, [Type])
764 go ty args = case tcSplitAppTy_maybe ty of
765 Just (ty', arg) -> go ty' (arg:args)
768 -----------------------
769 tcGetTyVar_maybe :: Type -> Maybe TyVar
770 tcGetTyVar_maybe ty | Just ty' <- tcView ty = tcGetTyVar_maybe ty'
771 tcGetTyVar_maybe (TyVarTy tv) = Just tv
772 tcGetTyVar_maybe other = Nothing
774 tcGetTyVar :: String -> Type -> TyVar
775 tcGetTyVar msg ty = expectJust msg (tcGetTyVar_maybe ty)
777 tcIsTyVarTy :: Type -> Bool
778 tcIsTyVarTy ty = maybeToBool (tcGetTyVar_maybe ty)
780 -----------------------
781 tcSplitDFunTy :: Type -> ([TyVar], [PredType], Class, [Type])
782 -- Split the type of a dictionary function
784 = case tcSplitSigmaTy ty of { (tvs, theta, tau) ->
785 case tcSplitDFunHead tau of { (clas, tys) ->
786 (tvs, theta, clas, tys) }}
788 tcSplitDFunHead :: Type -> (Class, [Type])
790 = case tcSplitPredTy_maybe tau of
791 Just (ClassP clas tys) -> (clas, tys)
792 other -> panic "tcSplitDFunHead"
794 tcInstHeadTyNotSynonym :: Type -> Bool
795 -- Used in Haskell-98 mode, for the argument types of an instance head
796 -- These must not be type synonyms, but everywhere else type synonyms
797 -- are transparent, so we need a special function here
798 tcInstHeadTyNotSynonym ty
800 NoteTy _ ty -> tcInstHeadTyNotSynonym ty
801 TyConApp tc tys -> not (isSynTyCon tc)
804 tcInstHeadTyAppAllTyVars :: Type -> Bool
805 -- Used in Haskell-98 mode, for the argument types of an instance head
806 -- These must be a constructor applied to type variable arguments
807 tcInstHeadTyAppAllTyVars ty
809 NoteTy _ ty -> tcInstHeadTyAppAllTyVars ty
810 TyConApp _ tys -> ok tys
811 FunTy arg res -> ok [arg, res]
814 -- Check that all the types are type variables,
815 -- and that each is distinct
816 ok tys = equalLength tvs tys && hasNoDups tvs
818 tvs = mapCatMaybes get_tv tys
820 get_tv (NoteTy _ ty) = get_tv ty -- Again, do not look
821 get_tv (TyVarTy tv) = Just tv -- through synonyms
822 get_tv other = Nothing
827 %************************************************************************
829 \subsection{Predicate types}
831 %************************************************************************
834 tcSplitPredTy_maybe :: Type -> Maybe PredType
835 -- Returns Just for predicates only
836 tcSplitPredTy_maybe ty | Just ty' <- tcView ty = tcSplitPredTy_maybe ty'
837 tcSplitPredTy_maybe (PredTy p) = Just p
838 tcSplitPredTy_maybe other = Nothing
840 predTyUnique :: PredType -> Unique
841 predTyUnique (IParam n _) = getUnique (ipNameName n)
842 predTyUnique (ClassP clas tys) = getUnique clas
846 --------------------- Dictionary types ---------------------------------
849 mkClassPred clas tys = ClassP clas tys
851 isClassPred :: PredType -> Bool
852 isClassPred (ClassP clas tys) = True
853 isClassPred other = False
855 isTyVarClassPred (ClassP clas tys) = all tcIsTyVarTy tys
856 isTyVarClassPred other = False
858 getClassPredTys_maybe :: PredType -> Maybe (Class, [Type])
859 getClassPredTys_maybe (ClassP clas tys) = Just (clas, tys)
860 getClassPredTys_maybe _ = Nothing
862 getClassPredTys :: PredType -> (Class, [Type])
863 getClassPredTys (ClassP clas tys) = (clas, tys)
864 getClassPredTys other = panic "getClassPredTys"
866 mkDictTy :: Class -> [Type] -> Type
867 mkDictTy clas tys = mkPredTy (ClassP clas tys)
869 isDictTy :: Type -> Bool
870 isDictTy ty | Just ty' <- tcView ty = isDictTy ty'
871 isDictTy (PredTy p) = isClassPred p
872 isDictTy other = False
875 --------------------- Implicit parameters ---------------------------------
878 isIPPred :: PredType -> Bool
879 isIPPred (IParam _ _) = True
880 isIPPred other = False
882 isInheritablePred :: PredType -> Bool
883 -- Can be inherited by a context. For example, consider
884 -- f x = let g y = (?v, y+x)
885 -- in (g 3 with ?v = 8,
887 -- The point is that g's type must be quantifed over ?v:
888 -- g :: (?v :: a) => a -> a
889 -- but it doesn't need to be quantified over the Num a dictionary
890 -- which can be free in g's rhs, and shared by both calls to g
891 isInheritablePred (ClassP _ _) = True
892 isInheritablePred (EqPred _ _) = True
893 isInheritablePred other = False
896 --------------------- Equality predicates ---------------------------------
898 substEqSpec :: TvSubst -> [(TyVar,Type)] -> [(TcType,TcType)]
899 substEqSpec subst eq_spec = [ (substTyVar subst tv, substTy subst ty)
900 | (tv,ty) <- eq_spec]
903 --------------------- The stupid theta (sigh) ---------------------------------
906 dataConsStupidTheta :: [DataCon] -> ThetaType
907 -- Union the stupid thetas from all the specified constructors (non-empty)
908 -- All the constructors should have the same result type, modulo alpha conversion
909 -- The resulting ThetaType uses type variables from the *first* constructor in the list
911 -- It's here because it's used in MkId.mkRecordSelId, and in TcExpr
912 dataConsStupidTheta (con1:cons)
913 = nubBy tcEqPred all_preds
915 all_preds = dataConStupidTheta con1 ++ other_stupids
916 res_ty1 = dataConOrigResTy con1
917 other_stupids = [ substPred subst pred
919 , let (tvs, _, _, res_ty) = dataConSig con
920 Just subst = tcMatchTy (mkVarSet tvs) res_ty res_ty1
921 , pred <- dataConStupidTheta con ]
922 dataConsStupidTheta [] = panic "dataConsStupidTheta"
926 %************************************************************************
928 \subsection{Predicates}
930 %************************************************************************
932 isSigmaTy returns true of any qualified type. It doesn't *necessarily* have
934 f :: (?x::Int) => Int -> Int
937 isSigmaTy :: Type -> Bool
938 isSigmaTy ty | Just ty' <- tcView ty = isSigmaTy ty'
939 isSigmaTy (ForAllTy tyvar ty) = True
940 isSigmaTy (FunTy a b) = isPredTy a
943 isOverloadedTy :: Type -> Bool
944 isOverloadedTy ty | Just ty' <- tcView ty = isOverloadedTy ty'
945 isOverloadedTy (ForAllTy tyvar ty) = isOverloadedTy ty
946 isOverloadedTy (FunTy a b) = isPredTy a
947 isOverloadedTy _ = False
949 isPredTy :: Type -> Bool -- Belongs in TcType because it does
950 -- not look through newtypes, or predtypes (of course)
951 isPredTy ty | Just ty' <- tcView ty = isPredTy ty'
952 isPredTy (PredTy sty) = True
957 isFloatTy = is_tc floatTyConKey
958 isDoubleTy = is_tc doubleTyConKey
959 isIntegerTy = is_tc integerTyConKey
960 isIntTy = is_tc intTyConKey
961 isBoolTy = is_tc boolTyConKey
962 isUnitTy = is_tc unitTyConKey
963 isCharTy = is_tc charTyConKey
966 = case tcSplitTyConApp_maybe ty of
967 Just (tc, [arg_ty]) -> tc == listTyCon && isCharTy arg_ty
970 is_tc :: Unique -> Type -> Bool
971 -- Newtypes are opaque to this
972 is_tc uniq ty = case tcSplitTyConApp_maybe ty of
973 Just (tc, _) -> uniq == getUnique tc
978 %************************************************************************
982 %************************************************************************
985 deNoteType :: Type -> Type
986 -- Remove all *outermost* type synonyms and other notes
987 deNoteType ty | Just ty' <- tcView ty = deNoteType ty'
992 tcTyVarsOfType :: Type -> TcTyVarSet
993 -- Just the *TcTyVars* free in the type
994 -- (Types.tyVarsOfTypes finds all free TyVars)
995 tcTyVarsOfType (TyVarTy tv) = if isTcTyVar tv then unitVarSet tv
997 tcTyVarsOfType (TyConApp tycon tys) = tcTyVarsOfTypes tys
998 tcTyVarsOfType (NoteTy _ ty) = tcTyVarsOfType ty
999 tcTyVarsOfType (PredTy sty) = tcTyVarsOfPred sty
1000 tcTyVarsOfType (FunTy arg res) = tcTyVarsOfType arg `unionVarSet` tcTyVarsOfType res
1001 tcTyVarsOfType (AppTy fun arg) = tcTyVarsOfType fun `unionVarSet` tcTyVarsOfType arg
1002 tcTyVarsOfType (ForAllTy tyvar ty) = (tcTyVarsOfType ty `delVarSet` tyvar)
1003 `unionVarSet` tcTyVarsOfTyVar tyvar
1004 -- We do sometimes quantify over skolem TcTyVars
1006 tcTyVarsOfTyVar :: TcTyVar -> TyVarSet
1007 tcTyVarsOfTyVar tv | isCoVar tv = tcTyVarsOfType (tyVarKind tv)
1008 | otherwise = emptyVarSet
1010 tcTyVarsOfTypes :: [Type] -> TyVarSet
1011 tcTyVarsOfTypes tys = foldr (unionVarSet.tcTyVarsOfType) emptyVarSet tys
1013 tcTyVarsOfPred :: PredType -> TyVarSet
1014 tcTyVarsOfPred (IParam _ ty) = tcTyVarsOfType ty
1015 tcTyVarsOfPred (ClassP _ tys) = tcTyVarsOfTypes tys
1016 tcTyVarsOfPred (EqPred ty1 ty2) = tcTyVarsOfType ty1 `unionVarSet` tcTyVarsOfType ty2
1019 Note [Silly type synonym]
1020 ~~~~~~~~~~~~~~~~~~~~~~~~~
1023 What are the free tyvars of (T x)? Empty, of course!
1024 Here's the example that Ralf Laemmel showed me:
1025 foo :: (forall a. C u a -> C u a) -> u
1026 mappend :: Monoid u => u -> u -> u
1028 bar :: Monoid u => u
1029 bar = foo (\t -> t `mappend` t)
1030 We have to generalise at the arg to f, and we don't
1031 want to capture the constraint (Monad (C u a)) because
1032 it appears to mention a. Pretty silly, but it was useful to him.
1034 exactTyVarsOfType is used by the type checker to figure out exactly
1035 which type variables are mentioned in a type. It's also used in the
1036 smart-app checking code --- see TcExpr.tcIdApp
1039 exactTyVarsOfType :: TcType -> TyVarSet
1040 -- Find the free type variables (of any kind)
1041 -- but *expand* type synonyms. See Note [Silly type synonym] above.
1042 exactTyVarsOfType ty
1045 go ty | Just ty' <- tcView ty = go ty' -- This is the key line
1046 go (TyVarTy tv) = unitVarSet tv
1047 go (TyConApp tycon tys) = exactTyVarsOfTypes tys
1048 go (PredTy ty) = go_pred ty
1049 go (FunTy arg res) = go arg `unionVarSet` go res
1050 go (AppTy fun arg) = go fun `unionVarSet` go arg
1051 go (ForAllTy tyvar ty) = delVarSet (go ty) tyvar
1052 `unionVarSet` go_tv tyvar
1054 go_pred (IParam _ ty) = go ty
1055 go_pred (ClassP _ tys) = exactTyVarsOfTypes tys
1056 go_pred (EqPred ty1 ty2) = go ty1 `unionVarSet` go ty2
1058 go_tv tyvar | isCoVar tyvar = go (tyVarKind tyvar)
1059 | otherwise = emptyVarSet
1061 exactTyVarsOfTypes :: [TcType] -> TyVarSet
1062 exactTyVarsOfTypes tys = foldr (unionVarSet . exactTyVarsOfType) emptyVarSet tys
1065 Find the free tycons and classes of a type. This is used in the front
1066 end of the compiler.
1069 tyClsNamesOfType :: Type -> NameSet
1070 tyClsNamesOfType (TyVarTy tv) = emptyNameSet
1071 tyClsNamesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` tyClsNamesOfTypes tys
1072 tyClsNamesOfType (NoteTy _ ty2) = tyClsNamesOfType ty2
1073 tyClsNamesOfType (PredTy (IParam n ty)) = tyClsNamesOfType ty
1074 tyClsNamesOfType (PredTy (ClassP cl tys)) = unitNameSet (getName cl) `unionNameSets` tyClsNamesOfTypes tys
1075 tyClsNamesOfType (PredTy (EqPred ty1 ty2)) = tyClsNamesOfType ty1 `unionNameSets` tyClsNamesOfType ty2
1076 tyClsNamesOfType (FunTy arg res) = tyClsNamesOfType arg `unionNameSets` tyClsNamesOfType res
1077 tyClsNamesOfType (AppTy fun arg) = tyClsNamesOfType fun `unionNameSets` tyClsNamesOfType arg
1078 tyClsNamesOfType (ForAllTy tyvar ty) = tyClsNamesOfType ty
1080 tyClsNamesOfTypes tys = foldr (unionNameSets . tyClsNamesOfType) emptyNameSet tys
1082 tyClsNamesOfDFunHead :: Type -> NameSet
1083 -- Find the free type constructors and classes
1084 -- of the head of the dfun instance type
1085 -- The 'dfun_head_type' is because of
1086 -- instance Foo a => Baz T where ...
1087 -- The decl is an orphan if Baz and T are both not locally defined,
1088 -- even if Foo *is* locally defined
1089 tyClsNamesOfDFunHead dfun_ty
1090 = case tcSplitSigmaTy dfun_ty of
1091 (tvs,_,head_ty) -> tyClsNamesOfType head_ty
1095 %************************************************************************
1097 \subsection[TysWiredIn-ext-type]{External types}
1099 %************************************************************************
1101 The compiler's foreign function interface supports the passing of a
1102 restricted set of types as arguments and results (the restricting factor
1106 tcSplitIOType_maybe :: Type -> Maybe (TyCon, Type)
1107 -- (isIOType t) returns (Just (IO,t')) if t is of the form (IO t'), or
1108 -- some newtype wrapping thereof
1109 -- returns Nothing otherwise
1110 tcSplitIOType_maybe ty
1111 | Just (io_tycon, [io_res_ty]) <- tcSplitTyConApp_maybe ty,
1112 -- This split absolutely has to be a tcSplit, because we must
1113 -- see the IO type; and it's a newtype which is transparent to splitTyConApp.
1114 io_tycon `hasKey` ioTyConKey
1115 = Just (io_tycon, io_res_ty)
1117 | Just ty' <- coreView ty -- Look through non-recursive newtypes
1118 = tcSplitIOType_maybe ty'
1123 isFFITy :: Type -> Bool
1124 -- True for any TyCon that can possibly be an arg or result of an FFI call
1125 isFFITy ty = checkRepTyCon legalFFITyCon ty
1127 isFFIArgumentTy :: DynFlags -> Safety -> Type -> Bool
1128 -- Checks for valid argument type for a 'foreign import'
1129 isFFIArgumentTy dflags safety ty
1130 = checkRepTyCon (legalOutgoingTyCon dflags safety) ty
1132 isFFIExternalTy :: Type -> Bool
1133 -- Types that are allowed as arguments of a 'foreign export'
1134 isFFIExternalTy ty = checkRepTyCon legalFEArgTyCon ty
1136 isFFIImportResultTy :: DynFlags -> Type -> Bool
1137 isFFIImportResultTy dflags ty
1138 = checkRepTyCon (legalFIResultTyCon dflags) ty
1140 isFFIExportResultTy :: Type -> Bool
1141 isFFIExportResultTy ty = checkRepTyCon legalFEResultTyCon ty
1143 isFFIDynArgumentTy :: Type -> Bool
1144 -- The argument type of a foreign import dynamic must be Ptr, FunPtr, Addr,
1145 -- or a newtype of either.
1146 isFFIDynArgumentTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1148 isFFIDynResultTy :: Type -> Bool
1149 -- The result type of a foreign export dynamic must be Ptr, FunPtr, Addr,
1150 -- or a newtype of either.
1151 isFFIDynResultTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1153 isFFILabelTy :: Type -> Bool
1154 -- The type of a foreign label must be Ptr, FunPtr, Addr,
1155 -- or a newtype of either.
1156 isFFILabelTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1158 isFFIDotnetTy :: DynFlags -> Type -> Bool
1159 isFFIDotnetTy dflags ty
1160 = checkRepTyCon (\ tc -> (legalFIResultTyCon dflags tc ||
1161 isFFIDotnetObjTy ty || isStringTy ty)) ty
1162 -- NB: isStringTy used to look through newtypes, but
1163 -- it no longer does so. May need to adjust isFFIDotNetTy
1164 -- if we do want to look through newtypes.
1166 isFFIDotnetObjTy ty =
1168 (_, t_ty) = tcSplitForAllTys ty
1170 case tcSplitTyConApp_maybe (repType t_ty) of
1171 Just (tc, [arg_ty]) | getName tc == objectTyConName -> True
1174 toDNType :: Type -> DNType
1176 | isStringTy ty = DNString
1177 | isFFIDotnetObjTy ty = DNObject
1178 | Just (tc,argTys) <- tcSplitTyConApp_maybe ty
1179 = case lookup (getUnique tc) dn_assoc of
1182 | tc `hasKey` ioTyConKey -> toDNType (head argTys)
1183 | otherwise -> pprPanic ("toDNType: unsupported .NET type")
1184 (pprType ty <+> parens (hcat (map pprType argTys)) <+> ppr tc)
1185 | otherwise = panic "toDNType" -- Is this right?
1187 dn_assoc :: [ (Unique, DNType) ]
1188 dn_assoc = [ (unitTyConKey, DNUnit)
1189 , (intTyConKey, DNInt)
1190 , (int8TyConKey, DNInt8)
1191 , (int16TyConKey, DNInt16)
1192 , (int32TyConKey, DNInt32)
1193 , (int64TyConKey, DNInt64)
1194 , (wordTyConKey, DNInt)
1195 , (word8TyConKey, DNWord8)
1196 , (word16TyConKey, DNWord16)
1197 , (word32TyConKey, DNWord32)
1198 , (word64TyConKey, DNWord64)
1199 , (floatTyConKey, DNFloat)
1200 , (doubleTyConKey, DNDouble)
1201 , (ptrTyConKey, DNPtr)
1202 , (funPtrTyConKey, DNPtr)
1203 , (charTyConKey, DNChar)
1204 , (boolTyConKey, DNBool)
1207 checkRepTyCon :: (TyCon -> Bool) -> Type -> Bool
1208 -- Look through newtypes
1209 -- Non-recursive ones are transparent to splitTyConApp,
1210 -- but recursive ones aren't. Manuel had:
1211 -- newtype T = MkT (Ptr T)
1212 -- and wanted it to work...
1213 checkRepTyCon check_tc ty
1214 | Just (tc,_) <- splitTyConApp_maybe (repType ty) = check_tc tc
1217 checkRepTyConKey :: [Unique] -> Type -> Bool
1218 -- Like checkRepTyCon, but just looks at the TyCon key
1219 checkRepTyConKey keys
1220 = checkRepTyCon (\tc -> tyConUnique tc `elem` keys)
1223 ----------------------------------------------
1224 These chaps do the work; they are not exported
1225 ----------------------------------------------
1228 legalFEArgTyCon :: TyCon -> Bool
1230 -- It's illegal to make foreign exports that take unboxed
1231 -- arguments. The RTS API currently can't invoke such things. --SDM 7/2000
1232 = boxedMarshalableTyCon tc
1234 legalFIResultTyCon :: DynFlags -> TyCon -> Bool
1235 legalFIResultTyCon dflags tc
1236 | tc == unitTyCon = True
1237 | otherwise = marshalableTyCon dflags tc
1239 legalFEResultTyCon :: TyCon -> Bool
1240 legalFEResultTyCon tc
1241 | tc == unitTyCon = True
1242 | otherwise = boxedMarshalableTyCon tc
1244 legalOutgoingTyCon :: DynFlags -> Safety -> TyCon -> Bool
1245 -- Checks validity of types going from Haskell -> external world
1246 legalOutgoingTyCon dflags safety tc
1247 = marshalableTyCon dflags tc
1249 legalFFITyCon :: TyCon -> Bool
1250 -- True for any TyCon that can possibly be an arg or result of an FFI call
1252 = isUnLiftedTyCon tc || boxedMarshalableTyCon tc || tc == unitTyCon
1254 marshalableTyCon dflags tc
1255 = (dopt Opt_UnliftedFFITypes dflags && isUnLiftedTyCon tc)
1256 || boxedMarshalableTyCon tc
1258 boxedMarshalableTyCon tc
1259 = getUnique tc `elem` [ intTyConKey, int8TyConKey, int16TyConKey
1260 , int32TyConKey, int64TyConKey
1261 , wordTyConKey, word8TyConKey, word16TyConKey
1262 , word32TyConKey, word64TyConKey
1263 , floatTyConKey, doubleTyConKey
1264 , ptrTyConKey, funPtrTyConKey